With little yet truly known about today's tragic bombing at the Boston Marathon besides the fact that a bombing took place, average folks are desperately seeking someone — anyone — to blame.

President Obama held a no-nonsense press conference moments ago where he promised to bring any responsible parties to justice, but clarified that they had no information yet on who those responsible parties might be. He expressed sympathy for the victims, stating that he and Michelle are sending their "deepest thought and prayers to the families of the victims," and assured us that Boston would have every single federal resource available to them. If only it didn't seem as if the President had addressed the nation in a time of tragedy far too many times in recent history.

Here's a growing list of local and national safety precautions and related interruptions taken in the aftermath of this afternoon's Boston Marathon bombing:

After one blast went off at the finish line of the Boston Marathon this afternoon, people—reporters and spectators—grabbed their cameras only to witness a second blast in nearly the same location. One of the first videos from the finish line (above) shows many runners collapsing from the trauma of the blast. Below, victims are shown being wheeled away from the scene.

At least two homemade bombs detonated at the finish line of the Boston Marathon in Copley Square just before 3 p.m. today, setting off explosions that killed three people and injured more than 100, many of whom lost limbs. According to early reports, three other explosive devices were found nearby, one of which was set off by police in a controlled detonation (a simultaneous fire at the JFK Library is said to have been unrelated). There are no suspects in custody, but police are searching for a person of interest who tried to gain access to a restricted area just before the bombs went off.

Two explosions rocked the finish line of the Boston Marathon today. Here are some of the latest photos from the scene. Warning: Some of these images, particularly the one at the bottom of this post, are graphic. [all photos via AP and Getty.]

Two explosions tore through downtown Boston today, killing at least three of the thousands of people who'd gathered to watch that city's famous marathon race. The explosions went off near the race's finish line, causing mass panic and ripping off people's limbs, according to early eyewitness accounts. Explosives units have been dispatched to investigate another suspicious device in the area as EMTs and doctors attend to the reportedly dozens of wounded.